单选题：One learns a language by making mistakes and ________them.[..

_______such heavy pollution already, it may now be too late to clean up the river.[ ]A. Having sufferedB. SufferingC. To sufferD. Suffered

He looked around and caught a man _____ his hand into the pocket of a passenger.A．putB．to be putC．to putD．putting

The next thing he saw was smoke ________ from behind the house.[ ]A. roseB. risingC. to riseD. risen

The country has already sent upthree unmanned spacecrafts, the most recent at the end of last March.[ ]A．has been launchedB．having been launchedC．being launched D．to be launched

Recently a survey ________ prices of the same goods in two different supermarkets has caused heateddebate among citizens.[ ]A. comparedB. comparingC. comparesD. being compared